Evidence From the Scene
The pest attacked the leaves, pods and beans. The leaves were bit on the outer part of the leaf. There were holes from the grasshopper. The plant was wilting with yellow leaves. There were holes in the pods where the beans were. This resulted in shrunken soybeans with stained spots from the bites.
Places That Were Damaged
Pictures of the Soybean Plant
I think that grasshoppers are the cause of the damage of to the plant. Grasshoppers mostly attack the pods and leaves of soybean plants. In the worst cases they can eat up to 60% of the foliage on beans.
The best time to spray for grasshoppers is when they are still in eggs or very early in development. Since they lay their eggs in soil, it is best to spray for them when the beans are small. Most of the time only 50% of the field needs to be sprayed. Since they are so mobile, grasshoppers touch most of the field. Carbaryl is the chemical to use.
Grasshoppers are hard to control since they jump so much. Chemical is the best idea, for cost and effectiveness.
Cost: about $20 per acre, only one spraying session would be needed. Since Carbaryl is the best kind of chemical available to use on grasshoppers it would be worth it.
Other alternative Options
A fungus (Entomophthora grylli) is fatal to grasshoppers. It is like a disease to them. However, it is only good to use when the weather is wet and grasshoppers love the hot and dry. Also, it only attacks specific kinds of grasshoppers.
If grasshoppers are bad the fall or late summer, it is a good indication that they will be a problem for the upcoming year. Area wide surveys may locate egg beds and other sites where early season activity originates.